1. Field of the Invention
The present invention relates to a lens fixer device for a scanner, particularly to a one-piece lens fixer device which is easy to adjust and fix the lens to an accurate position.
2. Description of Related Art
Currently, a lens fixer device for a document scanner can be classified as two types:
a) One-piece configuration
As shown in FIG. 1, an axial sectional view of a lens fixer device of prior arts, a lens holder 12 and a lens 10 are both of a cylindrical shape. The lens 10 is inserted into the holder 12 and fixed by three ribs (unshown on FIG. 1) formed on the cylindrical inner surface of the holder 12. The adjustment is performed by the assembly person to align the focused image through the lens 10 right on a CCD (charge couple device) 14 from which a waveform through an oscilloscope can be viewed. Generally, the holder 12 is a one-piece plastic element used for some basic or lower cost models of scanner. For the molding requirement, a departure angle is needed for the holder to depart from its injection mold, that means that the holder 12 is not a true cylinder but with a larger diameter at one end. Also, for the fastening purpose, a shrank portion 16 is formed inside the holder at a suitable position as shown in the figure. The aforesaid non-cylindrical shape of the holder 12 is easy to incline the lens 10 difficulting the same to perform a satisfactory adjustment with the CCD 14. It will then waste much labor and time for the adjustment.
b) Two-piece configuration
As shown in FIG. 2, a cross sectional view of another lens fixer device of prior arts, a lens 10 is fastened on a V-shaped base portion 22 by a separated cover 24 with two screws 26. The V-shaped base portion 22 makes the centering of the lens 10 easy and correct. The base portion 22 and the cover 24 are made of plastic or diecasting metal. They are suitable to be used in higher quality and price scanners. However, upon the adjusting and fastening process, the lens 10 is also easy to slide axially and miss the focus because the V-shaped base portion 22 and the cover 24 are two loose parts. Also, during the adjusting process, the lens moves easily for there is not any extra-pressure on the lens in the beginning. Therefore, a precise adjustment of the lens is still hard to make.